import random
strList=list('abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ')
strLen= len(strList)
verifyCode=[]
for i in range(4):
    verifyCode.append(strList[random.randint(0,strLen)])
print(''.join(verifyCode))